Method and apparatus for grinding ball seats in steel articles



March 28, 1944. o. R. BRINEY, JR

METHOD AND APPARATUS FOR GRINDING BALL SEATS IN STEEL ARTICLES Filed May21, 1942 l I B ISHHII I A INVENTOR. 077/5 7?. BIEM/EY 7?- FIGIG. zrf' TMI ATTO/PNE'YS Patented Mar. 28, 1944 METHOD AND APPARATUS FOR GRINDING.

BALL SEATS IN STEEL ARTICLES OttisR. Briney, Jr., Pontiac, Mich.

Application May 21, 1942, Serial No. 443,868

2 Claims.

This invention relates to an improved method of grinding or honing ballseats in metal articles and further to the apparatus employed in thepractice of such method.

One of the objects of the invention is to grind a spherical recess in amachine part by placing a dry, abrasive laden ball therein, then movingthe ball under pressure over the surface of the recess in an everchanging path.

Another object of the invention is to provide a ball which is formedfrom a material of a character capable of supporting an abrasive yetcapable of repeated use without appreciable loss of size and form.Exemplary of such material is a high carbon chrome alloy steelcarburized but not quenched or a steel ball of a similar alloy which ishardened and ground, then spheroidized or annealed.

Another, object of the invention is to charge or load the surface, of; ahoning ball with an abrasive by either violently tumbling av metalsphere .in a receptacle containing an abrasive flour or diamond powderor rolling a ball, under pressure between fiat horizontal steel plateshaving a coating of a dry abrasiveflour thereon.

A further object of the invention is to provide a platen for supportingand effecting the movement of the balls relative to, the work during thehoning operation. To this end the invention contemplates a pad formedfrom a material which offers a higher frictional surface. resistancethan that of the work, a material which possesses suificient resiliencyto. compensate for such irregularities in height as may occur inmounting a number of work pieces in the holder and a material which iscapable of being impregnated with the abrasive worn from the balls asthey are agitated in the work. A sheet of bonded comminuted cork hasbeen found, in practice, to provide such of the foregoing prerequisitesas are essential to the successful exercise of the improved honingmethod. Rubber or hard felt pads may also be used if desired.

Other objects and advantages more or less ancillary to the foregoing andthe manner in which all the various objects are realized will appear inthe following description, which considered in connection with theaccompanying drawing, sets forth the preferred embodiment of theinvention.

In the drawing which shows, for illustrative purpose only, one of theforms of apparatus that may be used in carrying out the method:

Fig. 1 is an elevational view of a fragmentary portion of a drill pressshowing the work holder mounted thereon;

Fig. 2 is a plan view of the work holder illustrated in Fig. 1;

Fig. 3 is a vertical sectional view throughv a portion of the workholder, the section being taken on a plane indicated by the line 3-3 inFig. 2;

Fig. 4 is a sectional view througha work piec which is typical of thetype, of product that can be finished by the improved method;

Fig. 5 is an elevational view, shown partially in section, of the.tumbling machine used in charging the honing balls; and

Fig. 6 is an elevational. view of an alternate form of mechanism used,in charging the honing balls.

Referring first to Fig. 4, thework piece chosen for the purpose ofillustration comprises. a carburized semi-finished steel body 10,machined with a reamed ball seat ll therein. End cutting tools, such asrose reamers despite the speeds and feeds employed in the use thereofare apt to score the work and leave concentric grooves and ribs whichobviously are subject to abnormal wear. Moreover, the contour of arecess is seldom spherical due to deformation of the Work in hardeningand the tendency of the tool or work to runf during machiningoperations.

As contemplated herein such irregularities in aball seat areabradedtherefrom by rolling a honing element in an ever changing pathover the surface of the ball seat and in addition by simultaneouslymoving the work in such a manner as to cause the ball to spin or twistwithin the recess. 7

In production the method of abraiding the ball seats is carried out byloading a plurality of work pieces ID in a holder or chuck l2; placing ahoning or grinding ball l3 in each recess, engaging the balls with asurface such as the cork pad l4 illustrated in Figs. 1 and 3, thenmoving the chuck relative to the pad under sufficient pressure to effecta rotative movement of the balls. The chuck preferably comprises a metaldisc drilled or recessed to support the work with the ball seat portionsthereof protruding from the face of the chuck in equidistant relation toeach other.

In contradistinction to a lapping operation which comprehends the use ofa fiuidic mixture of oil and emery and a porous or ductile lapping tool,the present invention contemplates a dry grinding process effectedthrough the medium by a tumbling machine comprising generallyvarotatively driven shaft l5 (Fig. 5) having a spider keyed thereon whichsupports a plurality of cups 5 providedwith removable caps or coverplates H. The cups I6 are partially filled with .the balls I 3 and theabrasive, sufficient space being left therein to permit the charge tofall against the end walls and sides of the cup during rotation and thusproduce a violent pounding and rubbing action between the balls andabrasive.-

An alternate method of charging the balls may be eii'ected by covering aflat steel plate such as shown in Fig. 6 with an abrasive floun placingone or' more balls thereon, then rotating under pressure a' second steelplate thereover;

After the chuck I2 is loaded with the work pieces and a honing ball isplaced in each recess therein the chuck is inverted and placed upon thepad 14 with theballs engaged "therewith. As shown in' Fig. 1, the pad ismounted upon the table I8 01' a'drillp'ress, the'spindle Hi thereofbeing provided with a crank arm having a pin 2| therein adapted forengagement within a recess 22 formed in the center ofthe chuck l2. Itwill be understood that the drill press shown herein is used merely inan illustrative sense and that numerous other-machines or mechanism maybe employed to drivethe chuck or pad without departing from the scope orspirit of the invention. The circumferential edge of th chuck is drilledfor the reception of a rod 24 which is designed to engage the column 25of the machine and effect the oscillation of the chuck during itsorbital movement over the pad M; The

rod is preferably constructed for detachable connection with the chuckinorder to accommodate the removal thereof during loading. If desiredthe free end of the rod maybe provided witha contractile spring 26mounted to maintain the rod in intimate relation with thecolurnn 25.

During the operation of the machine rotation of the'balls within'theirseats is effected by movement of the chuck by the traction ofiered bythe pad and by the weight and driving forces imposed upon the balls. Inaddition to the rotative movement of the balls the path or direction oftranslation and the rotative speed thereof will change as the chuck isoscillated about its axis while moving in th path described by themovement of the pin 2|. The tortuous paths described by the workpieceswill bring the balls therein into contact with the entire surface of therespective recesses and will, moreover, cause each ball to roll indirections transaxial to such concentric grooves and ribs as may havebeen formed by the reamer or cutting tool during the initial machiningoperation of the ball seats. I

In practice it has been found that by pressure rolling or pounding afine abrasive flour into the surface of a steel bal1 a dry honingelement can be produced which may be used over and over again before ithas to ,be discarded for loss of sizeor form.

Although the foregoing'description is" necessarily of a detailedcharacter, inorder that the inventionmay be completely set forth,- it isto be 'understood'that the specific terminology is not intended to berestrictve or confiningyand that various rearrangements of parts andmodifications of detail may b'e'resorted to without departing from thescope or spirit of the-invention 'as herein claimed. r

1. Mechanism for polishing bal1 seats in metal work pieces comprising,-astationary table a'pa'd thereon, a holder-for a pluralityof work-pieces,abrasive laden balls in the ball seats in the'work pieces in saidholder, engaged with said pad and constituting the support for theholder, a rota tively driven crank pivotally connected with said-holder,a stop adjacent said table and arocl on said holder yieldablyengaged with said stop for oscillating said holder about itspivotal-connection with said crank. a

2. Mechanism for polishing a ball seatlin-a metal work piece comprising,a stationary table, a work piece holder superjacent thereto, an abrasiveladen ball intermediate the table and the ball seat in a workpiece insaid holder a rotatively driven crank loosely connected with said holderand means for. moving said holder in a substantially oval..path. H v. i1

